1. Field of the Invention
The technical field of the present invention relates to a display device and a semiconductor device, a method for driving the same, and a method for manufacturing the same.
2. Description of the Related Art
In recent years, a display panel provided with a touch sensor has attracted attention. The touch sensor is classified by principle of operation under resistive touch sensors, capacitive touch sensors, optical touch sensors, and the like. In any of the sensors, an object is in contact with a display panel or in the vicinity of the display panel, whereby data can be input.
A display screen also serves as an input region by provision of a sensor (also referred to as a photosensor or a photoelectric conversion element) which detects light, as an optical touch sensor for a display panel.
In a display panel provided with a photosensor, light is emitted from the display panel to an object. The emitted light is reflected by the object to enter the photosensor. The photosensor generates current in accordance with luminance of the received light and data of an image of the object is obtained as electrical data.
As an example of a device provided with such a display panel, a display device having an image capturing function, that is, a so-called scanner function, which is provided with an area sensor that captures an image of an object, is given (e.g., see Patent Document 1).
Further, a technique for personal authentication with a touch sensor provided in a device which does not necessarily have a display panel, such as a fingerprint authentication device, has been proposed.